1. Field of the Invention
This invention relates to an antenna system for locating the direction of a signal source emitting microwave signals which utilizes two directional antennas designed for the same frequency and which have principal radiation lobes that are identical but are angularly offset relative to each other in the bearing plane so that the positional angle of the signal source can be determined within the overlap range by the use of signal level comparison or by means of quotient formation of the two received signals received by the two directional antennas.
2. Description of the Prior Art
Such an antenna system is disclosed in German LP No. 807,101. The system disclosed therein has two direction finding receiving antennas and the direction of signals received is identified by means of signal level comparison or by means of a quotient formation from the voltages from the two antennas in the major lobe range. However, overlapping side lobes also arise in the side lobe range of the individual antenna characteristic curves which gives rise to false bearings or ambiguities. With such system, there is no clear directional angle that can be allocated to a specific quotient value derived from the signal sources. Some false bearings and ambiguities can be suppressed by means of a further level comparison using the signals received with an omnidirectional antenna. If the omnidirectional signal level is always greater than the side lobe level of a directional antenna, then the electro-magnetic wave incident from the side lobe antennas is not evaluated for the direction finding. However, such systems require an additional receiver. If only a single receiver is used, the signal levels of the three antennas must be determined in chronological succession and not on a continuous basis.